Many sharks demonstrate a natural immunity to numerous forms of viral infection, even in the absence of a rapidly adapting immune system like ours. This observation got University of Pennsylvania geneticist Michael Zasloff thinking: what if researchers could identify the molecule (or molecules) responsible for conferring this antiviral characteristic?

"I was interested in sharks because of their seemingly primitive but effective immune system." Explains Zasloff. "No-one could explain why the shark was so hardy."

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The research team figured that a good place to start looking would be the protein squalamine. Since its discovery in the livers of dogfish sharks 1993, squalamine has received quite a bit of attention for its antibacterial and antitumorigenic properties.

Zasloff's team says it has yet to optimize squalamine dosing in any of the animal models, and therefore does not know the maximum therapeutic benefit that can be achieved using squalamine, but their initial results are very encouraging.

The researchers also note that squalamine has already been studied in several phase II clinical trials, and has a known safety profile in humans. Given this, the researchers emphasize how important it is that the broad antiviral properties of squalamine be investigated further.

"Squalamine appears to protect against viruses that attack the liver and blood tissues, and other similar compounds that we know exist in the shark likely protect against respiratory viral infections," explains Zasloff. He continues:

We may be able to harness the shark's novel immune system to turn all of these antiviral compounds into agents that protect humans against a wide variety of viruses. That would be revolutionary.

While many antibacterial agents exist, doctors have few antiviral drugs to help their patients, and few of those are broadly active.